Work will continue on the relationship between changes in vascular smooth muscle reactivity and Ca utilization during the development of hypertension in spontaneously hypertensive and DOCA hypertensive rats and their controls. Specifically, Ca45 content and Ca exchangeability will be analyzed in portal veins over a 4-16 week period and attempts will be made to resume changes in Ca45 content following stimulation with NE and K ion. A comparison of Ca2 ion antagonist action (D-600 and BAY-1040) will be made at the same time, to determine whether changes in Ca2 ion channels take place over this time period. BIBLIOGRAPHIC REFERENCES: C.R. Triggle, W.F. Grant and D.J. Triggle, "Intestinal Smooth Muscle Contraction and the effects of cadium and A 23187", J. Pharmacol. Exptl. Therap., 194, 182 (1975). D.J. Triggle and C.R. Triggle, "An Analysis of the Actions of Cations of the Lanthanide Series on The Mechanical Responses of Guinea-Pig Ileal Longitudinal Muscle", J. Physiol. (Lond), Jan. 1976. In press.